When Superman and Brainiac fall from Brainiac's control chair, the four walkways below them are all intact. After the camera angle changes, one of the walkways is destroyed.
When Brainiac's hologram disappears in a flash of light during his and Luthor's first meeting, if you use slow motion, you can see that the flash is actually a reused clip from the destruction of Krypton, complete with Krypton's moon in the foreground.
Superman recognized the Kryptonian script in Brainiac's ship, suggesting that the module his parents placed in his ship implanted a lot of knowledge about Krypton (again, as in Byrne's "Man of Steel"). This raises a question: did his memories of the death of Krypton come from Brainiac's orb (which seems awfully sloppy on Brainiac's part) or from the module his parents sent?
During the scene in which Brainiac first tries to convince Superman to join him, you can see a stylized image on the wall of Brainiac's ship that strongly resembles Brainiac from his classical appearance from the comic books, what with the bright green skin, and purple shirt complete with an oversized collar.
Superman: (after discovering that Brainiac destroyed every planet he visited) You destroyed those planets, didn't you? And every living soul on them!
Brainiac: Only their knowledge was important. It is what was programed to collect and protect.
Superman: But why kill?
Brainiac: The fewer beings who have the knowledge, the more precious it becomes.
Superman: You're insane!
Programmer: It'll take years to rebuild these systems.
Lex: You have two weeks.
Brainiac: I apologize for any discomfort, but it was important that I accurately gauged your powers.
Superman: Why? Morbid curiosity?
Brainiac: Curiosity, yes. Morbid, hardly. You see we have more in common than you could possibly know, Kal-El.
Superman: How do you know my name? Have you been to Krypton?
Brainiac: I am Krypton.
Councilman: So, Mr. Luthor, how long did you intend to keep your rendezvous a secret? In case you haven't heard there's a thing known as National Security.
Lex Luthor: There's also a thing known as Free Enterprise. It was LexCorp that scanned the heavens. It was LexCorp that made contact, and it will be LexCorp that reaps the benefits.
Superman is returning from a flight to Alpha Centauri in his escape rocket, which was modified by S.T.A.R. Labs in "The Main Man," suggesting that "Stolen Memories" may take place after "The Main Man."
Brainiac has been traveling throughout the Universe and gathering information about several planets since "The Last Son of Krypton."
This marks the first appearance of what will later be known as Superman's 'Fortress of Solitude.' It is located in the Arctic (as opposed to the Antarctic).
Music and Imagery
This episode contained several visual references to the old Max Fleischer Superman cartoons from the 1940's. The first one was Superman's battle with several robots which resembled those from the 1941 animated feature "The Mechanical Monsters" in both appearance and the manner in which they "gang up" on Superman. The second was when Brainiac attacked Superman with a laser blast, which Superman repelled by punching. In the debut animated feature "Superman" Superman also illogically repelled a mad scientist's laser blast by punching at it.